Process for producing liquid pig iron or semifinished steel products from iron-containing materials

ABSTRACT

In a method for producing liquid pig iron ( 9 ) or steel pre-products from fine-particulate iron-containing material ( 4 ) in a melter gasifier ( 1 ), the iron-containing material ( 4 ) is melted in a bed of solid carbon carriers ( 2 ) under supply of carbon-containing material ( 2 ) and oxygen-containing gas, at the simultaneous formation of a reducing gas, wherein the fine-particulate reduced material ( 4 ) and oxygen are introduced into the bed ( 20, 21 ) from the side. To be able to charge the fine-particulate iron-containing material to the melter gasifier ( 1 ) without a need for briquetting and, in doing so, avoid discharging of the fine-particulate iron-containing material ( 4 ) by the reducing gas formed in the melter gasifier ( 1 ), a fluidized bed ( 21 ) of fine-particulate solid carbon carriers ( 2 ) and fine-particulate iron-containing reduced material ( 4 ) is maintained above a fixed bed ( 20 ) formed of solid carbon carriers ( 2 ) and the fine-particulate reduced material ( 4 ) is charged into the fluidized bed ( 21 ) directly, in immediate contact with oxygen, preferably in the form of a strand having a ring-shaped cross-section and peripherally surrounding an oxygen jet and enclosing the oxygen, such that the oxygen is enclosed by the supplied fine-particulate reduced material ( 4 ), and the fine-particulate reduced material ( 4 ) is melted in the fluidized bed (FIG.  1 ).

The invention relates to a method for producing liquid pig iron or steelpre-products from fine-particulate iron-containing material,particularly reduced sponge iron, in a melter gasifier in which undersupply of carbon-containing material and oxygen at the simultaneousformation of a reducing gas the iron-containing material is melted in abed formed from solid carbon carriers, optionally upon previous completereduction, wherein the fine-particulate reduced material and oxygen areintroduced into the bed from the side, and to a plant for carrying outthe method.

EP-B-0 010 627 teaches a process for the production of liquid pig ironor steel pre-products from particulate iron-containing material,particularly prereduced sponge iron, and for the production of reducinggas in a melter gasifier, wherein by the addition of coal and by blowingin an oxygen-containing gas a fluidized bed is formed of coke particles.Here, the oxygen-containing gas or pure oxygen respectively are injectedinto the lower region of the melter gasifier. The particulateiron-containing material, particularly prereduced sponge iron, and thelumpy coal are fed in from above, through charging openings arranged inthe hood of the melter gasifier, the descending particles are sloweddown in the fluidized bed and the iron-containing particles are reducedand melted while falling through the coke fluidized bed. The molten andslag-covered metal collects at the bottom of the melter gasifier. Metaland slag are drawn off through separate tap openings.

A method of this kind is, however, not suited for processingfine-particle sponge iron, as fine-particle sponge iron would bedischarged from melter gasifier at once, due to the pronouncedupward-oriented gas flow existing within the same. Such a discharge ofthe fine-particle metal carriers is further favored by the temperatureprevailing in the upper region of the melter gasifier, i.e. in theregion above the melt-down gasifying zone, which is too low to ensure amelt-down, i.e. agglomeration of the fine particles at the charging siteto form bigger particles which in spite of the ascending gas streamcould sink down into the melt-down gasifying zone.

From EP-A-0 217 331 it is known to directly prereduce fine ore in afluidized bed process and to feed the prereduced fine ore to a meltergasifier and to completely reduce it by means of a plasma burner whilesupplying a carbon-containing reducing agent and to melt it. In themelter gasifier, a fluidized bed forms and thereabove a fluidized bed ofcoke. The prereduced fine ore or the sponge iron powder respectively aresupplied to a plasma burner provided in a lower section of the meltergasifier. One disadvantage here is that by feeding the prereduced fineore immediately in the lower melting region, i.e. in the region wherethe melt collects, complete reduction is no longer ensured and thechemical composition required for further processing of the pig ironcannot be achieved in any event. Moreover, charging of substantialamounts of prereduced fine ore is not feasible, due to the fluidized bedor fixed bed respectively forming from coal in the lower region of themelter gasifier, as it is not feasible to discharge a sufficient portionof the melting products from the high-temperature zone of the plasmaburner. Charging of more substantial amounts of prereduced fine orewould instantly lead to thermal and mechanical failure of the plasmaburner.

From EP-B-0 111 176 it is known to produce sponge iron particles andliquid pig iron from lumpy iron ore, the iron ore being directly reducedin a direct-reduction aggregate and sponge iron particles dischargedfrom the direct-reduction aggregate being separated into a coarse-andfine-grain fraction. The fine-grain fraction is supplied to a meltergasifier, in which the heat required for melting the sponge iron as wellas the reducing gas supplied to the direct-reduction aggregate areproduced from charged coal and supplied oxygen-containing gas. Thefine-grain fraction is conducted into the melter gasifier via a downpipeprojecting from the head of the melter gasifier as far as into thevicinity of the fluidized bed of coal. At the end of the downpipe abaffle plate is provided in order to minimize the velocity of thefine-grain fraction, and consequently the exit velocity of thefine-grain fraction on leaving the downpipe is very low. At the chargingsite, the temperature reigning inside the melter gasifier is very low,as a result of which immediate melting of the supplied fine-grainfraction cannot take place. This and the low exit velocity from thedownpipe lead to a substantial portion of the supplied fine-grainfraction exiting from the melter gasifier along with the reducing gasproduced in the same. In accordance with this process it is not possibleto charge a more substantial amount of fine grain or to charge finegrain exclusively.

In a process according to EP-A-0 576 414 lumpy iron-ore-containingcharging substances are directly reduced in a reduction shaft furnace,by means of the reducing gas formed in the meltdown gasifying zone. Thesponge iron thus obtained is subsequently fed to the meltdown gasifyingzone. In order to be able to additionally utilize fine ore and/or oredust, such as oxidic iron fine dust incurring in a metallurgical plant,with this known process, the fine ore and/or the ore dust along withsolid carbon carriers are supplied to a dust burner working into themeltdown gasifying zone and are reacted in a substoichiometriccombustion reaction. A process of this kind enables efficient processingof fine ore and/or ore dust incurring in a metallurgical plant, and thatup to an order of magnitude of 20 to 30% of the total ore charge, andthus enables a combined processing of lumpy ore and fine ore. Adisadvantage associated with this process is that regions with an excessof metal and regions with an excess of carbon may result in themelt-down gasifying zone.

From EP-A-0 493 752 it is known to separate hot dusts from agasification reactor, such as a melter gasifier, in a cyclone and inorder to surmount a difference of pressure between the cyclone and thegasifier recirculate them via a sluice system, namely via a burner. Theknown sluice system is very expensive in construction, the mechanicallyoperated sluices being moreover exposed to substantial wear by thedustlike solids.

From EP-A-0 594 557, a method of the initially described kind is knownwherein a sponge iron fine grain fraction by means of a conveying gas ischarged directly into the fluidized bed formed by the melt-downgasifying zone in the melter gasifier. However, this is disadvantageous;clogging of the fluidized bed may ensue, leading to insufficient gascirculation and optionally to damming-up of gas and subsequently toeruptive outbreaks of gas, by which the clogged fluidized bed is brokenup. Hereby, the gasification process for the carbon carriers and alsothe melt-down process for the reduced iron ore are markedly disturbed.

The invention aims at avoiding these disadvantages and difficulties andhas as its object to provide a method of the initially described kindand a plant for carrying out the method, with said method and plantallowing the processing of fine-particulate iron-containing and at leastpartially reduced material without any need for briquetting and wherein,on the one hand, discharging of the supplied fine particles by thereducing gas generated in the melt-down-gasifying zone is reliablyavoided and, on the other hand, the gasification process can proceeduntroubled by the fine-particulate reduced material which is beingcharged. This means that burdening the melt-down gasifying zone with thefine-particulate iron-containing reduced material is to be avoided, evenin cases where up to 100% fine-particulate iron-containing reducedmaterial are charged into the melter gasifier.

In accordance with the invention, this object is achieved in that abovea fixed bed formed of solid carbon carriers a fluidized bed offine-particulate solid carbon carriers and fine-particulateiron-containing reduced material is maintained and the fine-particulatereduced material is charged into the fluidized bed directly, inimmediate contact with oxygen, preferably in the form of a strand havinga ring-shaped cross-section and peripherally surrounding an oxygen jetand enclosing the oxygen, and that the fine-particulate reduced materialis melted in the fluidized bed.

According to a preferred embodiment, the fine-particulate reducedmaterial is charged into the fluidized bed by means of a fluidizing gas,preferably by being blown in.

In order to use the center of the fluidized bed as a melting zone aswell, oxygen preferably is additionally blown into the fluidized bed(21) in the central region of the same, preferably from above.

It is advantageous, especially when larger amounts/unit of time offine-particulate reduced material have to be processed, if thefine-particulate reduced material is blown into the fluidized bed underpressure by means of a conveying gas, such that at the outlet into thefluidized bed there forms a hollow space which is free for thefine-particulate reduced material.

To balance a difference in pressure between the feeding of the reducedfine-particulate material and the melt-down gasifying zone, thefine-particulate reduced material prior to being charged into thefluidized bed (21) is suitably collected in a vessel under formation ofa fluidized bed and out of the fluidized bed is conveyed onward into thefluidized bed by means of a conveying and/or fluidizing gas. Herein, thefluidized bed forms a sluice maintaining the difference in pressure.

Herein, a conveying gas for the fine-particulate reduced material issuitably fed into the fluidized bed under pressure, preferably at apressure exceeding the pressure that prevails in the fluidized bed.

A plant for carrying out the method, comprising a melter gasifier havingsupply and discharge ducts for adding carbon-containing material,iron-containing reduced fine-particulate material, for withdrawing thegenerated reducing gas and for feeding oxygen, and further comprising atap for slag and iron-melt is characterized in that a lower section ofthe melter gasifier serves for collecting the molten pig iron and theliquid slag and a superimposed central section for accommodating a fixedbed of solid carbon carriers and subsequently an upper section foraccommodating a fluidized bed and that a calming space is providedthereabove, that at the level of the fluidized bed at least one mouth ofa conveying duct for fine-particulate reduced material is provided inthe side wall of the melter gasifier and that an oxygen supply ductpenetrates the conveying duct for the fine-particulate reduced materialcentrally, forming a ring-shaped conveying space for thefine-particulate reduced material, and runs into the melter gasifier.

Preferably, a fluidizing gas for the fine-particulate reduced materialcan be admitted to the conveying duct.

To enhance the effectiveness of melting the reduced material within thefluidized bed it is advantageous if, in addition, there projects intothe melter gasifier an oxygen supply lance whose outlet opening for theoxygen assumes a position at the level of the fluidized bed and centralwith respect to the cross-section.

To maintain the difference in pressure between the feeding of thefine-particulate reduced material and the melter gasifier, the conveyingduct for the fine-particulate reduced material suitably runs to themelter gasifier via a fluidized bed sluice.

Advantageously, a duct supplying a conveying gas for thefine-particulate reduced material runs into the fluidized bed sluice.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings, each of FIGS. 1 and 2 schematically illustratea melter gasifier in vertical section.

DESCRIPTION OF PREFERRED EMBODIMENTS

In a melter gasifier 1, a reducing gas is generated from solidcarbon-containing material 2, such as coal, and from oxygen-containinggas by gasifying the coal 2, which reducing gas through a discharge duct3 is conducted to a fluidized bed reactor (not illustrated in detail) inwhich fine ore is reduced to sponge iron 4. The melter gasifier 1 isprovided with a feed duct 5 for the solid carbon carriers 2, a feed duct6 for oxygen-containing gases, a feed duct 7 for sponge iron as well asoptionally feed ducts for carbon carriers, such as hydrocarbons, thatare liquid or gaseous at room temperature and for burnt fluxes. In themelter gasifier 1 molten pig iron 9 and molten slag 10 collect in thebottom area 8, which are tapped off through a tap 11.

The iron ore that has been reduced to sponge iron 4 in the fluidized bedreactor is discharged from the fluidized bed reactor—optionally togetherwith burnt fluxes—via a conveying means, for example by means ofdischarge worms, and is fed to the melter gasifier 1. Both the feed duct5 for the solid carbon carriers 2 and the discharge duct 3 for thereducing gas, namely a plurality of each, are provided in the dome area12 of the melter gasifier 1 in a roughly radially symmetricalarrangement.

The discharge duct 3 opens into a solids separator 13 constructed as ahot cyclone. In this hot cyclone 13 the fine particles 14 entrained bythe reducing gas, such as coal and sponge iron, are separated and via adownpipe 15 are introduced into a fluidized bed sluice 16. Into thisfluidized bed sluice 16 there enters a feed duct 17 for reducedfine-particulate material, namely for the sponge iron 4 that is formedfrom fine ore and that is withdrawn from the fluidized bed reactor.

The fluidized bed 18 formed in the fluidized bed sluice 16 from thelower reaches of the hot cyclone and the supplied fine-particulatesponge iron 4 is maintained by means of a fluidizing gas supplied to thefluidized bed sluice 16 via a tuyere bottom 19.

From the fluidized bed sluice 16 the feed duct 7 for the sponge iron 4leads into the melter gasifier 1 at the height-level of the fluidizedbed 21 formed in the melter gasifier 1 above a fixed bed 20 ofcarbon-containing material. This fluidized bed 21 is formed offine-particulate carbon-containing material 2 and sponge iron 4. Thecarrier gas for maintaining the fluidized bed 21 is formed by thereducing gas exiting the fixed bed 20, which reducing gas is generatedby the gasification of the carbon-containing material 2.

To the feed duct 7 constructed as a conveying duct for the sponge iron4, a fluidizing gas is admitted at least in the outlet area 22, whichgas conveys the sponge iron 4 into the melter gasifier 1. At a centralposition inside the conveying duct 7 and coaxial therewith an oxygenfeed duct 23 is provided whose outlet 24 projects into the meltergasifier 1 to just beyond the ring-shaped outlet 25 of the conveyingduct 7. The oxygen jet fed in through the oxygen feed duct 23 isperipherally surrounded, i.e. enclosed, by the supplied sponge iron 4.As a consequence, melting of the sponge iron 4 will occur directly inthe fluidized bed 21 on account of the high temperature that adjusts.

Preferably, several fluidized bed sluices 16 are disposed around themelter gasifier 1 in a distributed arrangement, whereby feeding of thesponge iron 4 will be radially symmetrical and will be uniformthroughout the cross-section of the melter gasifier 1. Between theoutlets 25 of the sponge-iron conveying ducts 7 still further oxygenfeed ducts 26 may, in addition, open into the melter gasifier 1, whichfurther enhance the effectiveness of the melting operation. To alsoutilize the center of the fluidized bed 21 as a melting zone there isprovided an oxygen lance 27 whose outlet 28 is provided to be locatedapproximately in the center and closely above the fixed bed 20 in thefluidized bed 21. The oxygen lance 27 suitably is arranged so as toproject into the melter gasifier 1 centrally from above.

The total height 29 of the fixed bed 20 and the fluidized bed 21 isadjusted such that a reducing gas temperature of about 1050° C. willadjust in the calming space 30 provided above the fluidized bed 21. Theposition of the fixed-bed surface can be influenced by the choice of thegrain size of the coal which is being supplied and/or by thedistribution of the total oxygen content among the fixed bed 20 and thefluidized bed 21.

According to the embodiment represented in FIG. 2, feeding is effectedinto the upper portion of the fluidized bed sluice 16 via a duct 31 bymeans of a conveying gas formed f i. of cooled reducing gas, and in anamount such that at the outlet 25 a hollow space 32 will form in thefluidized bed 21 on account of the impulse of the entering gas.

The invention is not limited to the embodiments represented in thedrawing but may be modified in various respects. There is f.i. no needfor the oxygen feed duct 23 to be provided coaxially inside the feedduct 7. What is essential is that there be contact with oxygen directlyafter the sponge iron 4 has entered the melter gasifier 1, so that themelting process of the sponge iron 4 can take place entirely in thefluidized bed 21. To achieve this, the feed duct 7 and the oxygen feedduct 23 could be arranged so as to be immediately adjacent, although thebest result is attained if the sponge iron 4 encloses the oxygen jet atleast in the region of the outlet 25.

What is claimed is:
 1. A plant for producing liquid pig iron (9) orsteel pre-products from fine-particulate reduced iron-containingmaterial (4), comprising a melter gasifier (1) having supply anddischarge ducts (3, 5, 6, 7) for adding carbon-containing material (2),iron-containing reduced fine-particulate material (4), for withdrawingthe generated reducing gas and for feeding oxygen, and furthercomprising a tap (11) for slag and iron-melt, characterized in that alower section (8) of the melter gasifier (1) serves for collecting themolten pig iron (9) and the liquid slag (10) and a superimposed centralsection for accommodating a fixed bed (20) of solid carbon carriers andsubsequently an upper section for accommodating a fluidized bed (21) andthat a calming space is provided there above, that at the level of thefluidized bed (21) at least one mouth of a conveying duct (7) forfine-particulate reduced material (4) is provided in the side wall ofthe melter gasifier (1) and that an oxygen supply duct (23) is providedin immediate proximity to the conveying duct (7) for fine-particulatereduced material (4), wherein said conveying duct (7) runs to the meltergasifier via a fluidized bed sluice, and that a duct (31) supplying aconveying gas for the fine-particulate reduced material (4) runs intothe fluidized bed sluice (16).
 2. A plant according to claim 1,characterized in that to the conveying duct (7) for the fine-particulatereduced material (4) a fluidizing gas can be admitted.
 3. A plantaccording to claim 1, characterized in that, in addition, there projectsinto the melter gasifier (1) an oxygen supply lance (27) whose outletopening (28) for the oxygen assumes a position at the level of thefluidized bed (21) and central with respect to the cross-section.
 4. Amethod for producing liquid pig iron (9) or steel pre-products fromfine-particulate iron-containing material (4) in a melter gasifier (1)in which under supply of carbon-containing material (2) and oxygen atthe simultaneous formation of a reducing gas the iron-containingmaterial (4) is melted in a bed (20, 21) formed from solid carboncarriers (2), upon previous complete reduction, wherein thefine-particulate reduced material (4) and oxygen are introduced into thebed (20, 21) from the side, characterized in that above a fixed bed (20)formed of solid carbon carriers (2) a fluidized bed (21) offine-particulate solid carbon carriers (2) and fine-particulateiron-containing reduced material (4) is maintained and thefine-particulate reduced material (4) is charged into the fluidized bed(21) directly, in immediate contact with oxygen and that thefine-particulate reduced material (4) is melted in the fluidized bed,wherein the fine-particulate reduced material (4) prior to being chargedinto the fluidized bed (21) is collected in a vessel (16) underformation of a fluidized bed (18), the vessel thereby forming afluidized bed sluice, and out of the fluidized bed (18) is conveyedonward into the fluidized bed (21) by a conveying and/or fluidizing gas;and the reducing gas formed together with fine-particulate materialcarried thereby is discharged from the melter gasifier via a cycloneseparator and the fine-particulate material separated therein is fedinto the melter gasifier by means of said fluidized bed sluice, togetherwith the fine-particulate reduced material.
 5. A method according toclaim 4, characterized in that the fine-particulate reduced material (4)is charged into the fluidized bed (21) by means of a fluidized gas.
 6. Amethod according to claim 5, wherein the fluidized gas is blown into thefluidized bed.
 7. A method according to claim 4, characterized in thatoxygen is additionally blown into the fluidized bed (21) in the centralregion of the same.
 8. A method according to claim 7, wherein the oxygenis blown into the fluidized bed (21) from above.
 9. A method accordingto claim 4, characterized in that the fine-particulate reduced material(4) is blown into the fluidized bed (21) under pressure by means of aconveying gas, such that at the outlet into the fluidized bed (21) thereforms a hollow space (32) which is free for the fine-particulate reducedmaterial (4).
 10. A method according to claim 9, characterized in thatinto the fluidized bed (18) a conveying gas for the fine-particulatereduced material (4) is fed under pressure.
 11. A method according toclaim 10, wherein said conveying gas is fed into the fluidized bed (18)under a pressure exceeding the pressure that prevails in the fluidizedbed (21).